After removing images, editor should remove selection

[Former user]

Steps to reproduce error:

• select more than one images from the end of the FPG
• delete selected images

You will see the selection indicator is pointing to an empty space in the FPG. It should disappear.

Also, if you want to add images right after removing, the editor will crash because it wont be able to find the image to replace with the new one.

[Darío Cutillas Carrillo]

fix #21

→ <<cset 7fa705536921>>